Precision pump



United States Patent 3,136,455 PRECISION PUMP Loring Coes, Jr.,Princeton, Mass., assignor to Norton Company, Worcester, Mass, acorporation of Massachusetts Filed Aug. 10, 1-961, Ser. No. 130,571 5Claims. (Cl. 222319) This invention relates to precision pumps, and,more especially to pumps for feeding fluid in small amounts with a highdegree of accuracy, both as to the quantity and rate of feed.

Industry is requiring, more-and-more, means for supplying fluid in smallmeasured quantities at a very low rate of feed however there are nocommercially available devices satisfactory for this purpose.Conventional displacement pumps do not provide very high accuracy andare eflected adversely by small amounts of dirt; gear pumps do notprovide a constant output and are subject to vapor-lock which stopsdelivery; and peristaltic pumps are subject to deterioration andinaccuracy due to temperature changes. Valves are impractical because ofthe difliculty of reproduction and the tendency of tiny openings tobecome blocked by gas, bubbles, droplets, dirt and the like.. A commongas rotameter has been used to control the rate of flow however at lowrates of flow they are more eifected by viscosity, friction and thepresence of bubbles than they are by the actual flow. Moreover, they arerestricted in use to mere atmospheric conditions. The foregoing and suchother means as are available are g the accompanying drawing which is anelevation of the for the most part unreliable for flow below 5cubic-cen'timeters per minute.

The objects of this invention are to provide a precision pump fordelivering fluid in accurate amounts and at accurate rates; to provide apump which will maintain a high degree of accuracy at low rates of flow,for example at cubic centimeter per minute and less; to provideapparatus in which the delivery is not effected by dirt, or

As herein illustrated, the pump comprises a barrel having a well forholding a quantity of liquid, a discharge opening at the upper end ofthe well through which the liquid in the well may be ejected bydisplacement from the well, a piston supported in the barrel formovement into the well, and means for moving the piston into the well ata precisely controlled rate and a predetermined amount, the pistonoperating to displace a Volume of liquid from the well through theopening which is equal to that portion of the piston moved into theWell. There is a duct connected to the discharge opening for conductingthe liquid to a place of use and there is means associated therewith tomaintain the pressure within the pump barrel equal to that at thedischarge end of the duct. The upper end of the barrel has a glandthrough which the means for supporting the piston passes and the latteris flexible element in the form of a cord, connected at one end to theupper end of the piston and at its opposite end to a supporting pulley.Intermediate the supporting pulley and the gland the cord is wound oncearound the drive pulley of a timing motor, the latter being operable topay the cord out at a predetermined rate and/or amount. There is afilling opening in the barrel above the well, a duct connected theretoand to a reservoir, and a valve cock operable to permit flow of fluidfrom the reservoir into the barrel to refill the well.

The apparatus will now be described with reference to pump partly insection.

The pump comprises a cylindrical barrel 10' supported by a horizontallydisposed clamp 12, the latter being mounted for vertical adjustment onspaced parallel rods 1414 fixed at their lower ends in a suitable rigidbase 16. Set screws 18 are provided for fixing the clamp at a suitableheight on the rods. The upper ends of the rods are fastened to the rearside of a headblock 20.

The pump barrel 10 is closed at its ends and is comprised of upper andlower parts 22 and 24, the lower part 22 containing a well 26 forholding a quantity of fluid, which is adapted to be displaced therefromby downward movement of a piston P suspended in the upper part above thewell. A discharge opening 28 is provided in the wall of the barrel, atthe top of the well, through which liquid in the well may be dischargedby lowering the piston in the well as will appear hereinafter. A duct 30is connected at one end to the discharge opening and at its other end toa discharge nozzle 32 at the lower end of the barrel. As herein shown,the nozzle 32 is formed integral with the lower end of the barrelhowever it may be a separate element attached to the duct 30, which maybe flexible so that the nozzle can be moved relative to the barrel forinserting it into the mouth of a receptacle or inlet opening in thesystem to which the fluid is to be delivered. The nozzle contains anorifice 34. A vent tube 36 is connected at its upper end to the duct30at the upstream side of the orifice and at its lower end to the nozzleat the downstream side of the orifice.

This construction provides for maintaining the same pressure within thepump barrel as the vessel or system to which the fluid is beingdelivered so that back pressure developed in the vessel or system willnot interfere with free-flow of the liquid.

The barrel has an inlet opening 38 above the discharge opening 38 towhich there is connected the lower end of a duct 40, through whichliquid may be supplied to the barrel to refill the well. The duct 40 isconnected at its upper end to a vessel42 for holding a reserve quantityof liquid and there is a valve cock 44 in the duct by means of which theliquid may be allowed to flow from the vessel into the barrel to fillthe well and then shut to maintain a pressure within the barrelcorresponding to that at the end of the nozzle.

The upper part of the barrel 24 is in the form of a closure cap whichhas an upwardly extending gland 46 comprised of an outer tube 48 and aninner tube 50. The inner tube is in communication with the inside of thebarrel of the pump. The annular space between the tubes 48 and 50 ispartially filled with mercury 52. A tube 54 having a cap 56 at its upperend is disposed in the annular space between the tubes 48 and 50 so thatits lower end is submerged within the body of mercury. A flexible cord58 is attached to the inner side of the cap 56 and extends downwardlythrough the tube 50 into the barrel where it is attached to the upperend of the piston P. A flexible cord 60 is attached to the upper side ofthe cap 56, is wound once around a drive pulley 62 on a timer motor 64mounted on the headblock 20 and over a supporting pulley 66 also mountedon the headblock, to which it is attached at 68. A weight W is suspendedby a cord 70 on the support pulley as to counterbalance the weight ofthe piston in the barrel. The timer motor is connected to a suitablesource of power by way of a switch 72 and is operable to turn the drivepulley 62 in a direction tolower the piston P into the well 26.

The piston P is of known dimensions hence lowering it into the liquidwithin the well will discharge a corresponding volume of liquid from thewell through the duct 30 to the nozzle 32. 7

By using a pulley 62 of known diameter D and a piston P of knowndiameter D the rate of discharge in cubiccentimeters per minute may bedetermined by the formula wherein N is the number of revolutions perminute and R is the rate of feed.' Pumping rates of 0.1 cc. per minuteand less can be accurately controlled with this apparatus. The rate maybe varied by changing .the diameter of the pulley 62 or the piston P.

The pump may be made of metal where corrosion is not a factor to beconsidered, however, if it is, metal alloys, glass, plastic, ceramic andthe like, which are resistant to corrosion may be used. Since the pumpdoes not contain valves or other closely fitting moving parts,temperature changes, pressure changes, the inadvertent presence of a fewdirt particles and the like have no influence on its accuracy or uponthe rate or amount of flow at very low'velocity and in very smallamounts. Moreover, the venting makes the pump independent of backpressure. Other advantages are that the pump is of simple construction,durable and easy to use.

It should be understood that the present disclosure is for the purposeof illustration only and that this invention includes all modificationsand equivalents which fall within the scope of the appended claims.

I claim:

1. A precision pump for supplying measured quantities of liquid at apredetermined rate comprising a two-part barrel, the lower partproviding a well for holding a liquid and containing a discharge openingat a predetermined level from the bottom, means for supplying liquid -tothe well, a filling opening at a higher level, an injection nozzle atits lower end containing an orifice, andducts connecting the dischargeopening to the nozzle at both sides of the orifice, the upper partconstituting a closure for-the barrel and mounting a gland, a flexibleelement extending through the gland into the barrel above the well, apiston connected to the end of the flexible element within the barrel,means supporting that portion of the flexible element externally of thebarrel, and'a timer motor including a drive pulley about which a portionof the flexible element is wrapped operable to pay off the element at apredetermined rate.

2. A precision pump for supplying measured quantities of liquid at ameasured rate comprising a barrel having a Well for holding a quantityof liquid, means for supplying liquid to the well, a discharge openingat the upper end of the well through which liquid in the Well may beejected by displacement from the well, a piston supported in the barrelfor movement into the well, means for moving the piston into the well ata precisely controlled rate, said piston operating to displace a volumeof liquid from the well through the opening which volume is equal tothat portion of the piston moved into the well, and a nozzle disposedbelow the level of the discharge opening of the barrel, a ductconnecting the discharge opening to the nozzle, and a by-pass ductconnected at one end upstream of the orifice. andtat its'other enddownstream of the orifice.

3. A precision pump according to claim 2, wherein there is aliquid-sealed gland at the upper end of the barrel and the support forthe piston is a flexible element which extends through the gland intothe barrel.

4. A precision pump according to claim 2, wherein there is a gland atthe top of the barrel, the support for the piston is a cord passingthrough the gland, there is a timer motor including a drive pulleydriven thereby and the cord is wrapped on the drive pulley for payingout at a measured rate.

5. A precision pump according to claim 2, wherein there is a gland atthe top of the barrel, the support for the piston is a cord passingthrough the gland, there is a supporting pulley on which the cord isfastened, a timer motor having a driving pulley about which a' portionof the cord between the gland and the supporting pulley is wrapped for'paying out at a measured rate, and a weight connected to the supportingpulley to counterbalance the piston.

References Cited in the file of this patent UNITED STATES PATENTS

1. A PRECISION PUMP FOR SUPPLYING MEASURED QUANTITIES OF LIQUID AT APREDETERMINED RATE COMPRISING A TWO-PART BARREL, THE LOWER PARTPROVIDING A WELL FOR HOLDING A LIQUID AND CONTAINING A DISCHARGE OPENINGAT A PREDETERMINED LEVEL FROM THE BOTTOM, MEANS FOR SUPPLYING LIQUID TOTHE WELL, A FILLING OPENING AT A HIGHER LEVEL, IN INJECTION NOZZLE ATITS LOWER END CONTAINING AN ORIFICE, AND DUCTS CONNECTING THE DISCHARGEOPENING TO THE NOZZLE AT BOTH SIDES OF THE ORIFICE, THE UPPER PARTCONSTITUTING A CLOSURE FOR THE BARREL AND MOUNTING A GLAND, A FLEXIBLEELEMENT EXTENDING THROUGH THE GLAND INTO THE BARREL ABOVE THE WELL, APISTON CONNECTED TO THE END OF THE FLEXIBLE ELEMENT WITHIN THE BARREL,MEANS SUPPORTING THAT PORTION OF THE FLEXIBLE ELEMENT EXTERNALLY OF THEBARREL, AND A TIMER MOTOR INCLUDING A DRIVE PULLY ABOUT WHICH A PORTIONOF THE FLEXIBLE ELEMENT IS WRAPPED OPERABLE TO PAY OFF THE ELEMENT AT APREDETERMINED RATE.